86 lines
2.1 KiB
C
86 lines
2.1 KiB
C
/*
|
|
(c) copyright 1988 by the Vrije Universiteit, Amsterdam, The Netherlands.
|
|
See the copyright notice in the ACK home directory, in the file "Copyright".
|
|
*/
|
|
|
|
/* $Header$ */
|
|
|
|
/*
|
|
CONVERTS FLOATING POINT TO EXTENDED FORMAT
|
|
|
|
Two sizes of FLOATING Point are known:
|
|
SINGLE and DOUBLE
|
|
*/
|
|
/********************************************************/
|
|
/*
|
|
It is not required to normalize in extended
|
|
format, but it has been chosen to do so.
|
|
Extended Format is as follows (at exit):
|
|
|
|
->sign S000 0000 | 0000 0000 <SIGN>
|
|
->exp 0EEE EEEE | EEEE EEEE <EXPONENT>
|
|
->m1 LFFF FFFF | FFFF FFFF <L.Fraction>
|
|
FFFF FFFF | FFFF FFFF <Fraction>
|
|
->m2 FFFF FFFF | FFFF FFFF <Fraction>
|
|
FFFF F000 | 0000 0000 <Fraction>
|
|
*/
|
|
/********************************************************/
|
|
|
|
#include "FP_bias.h"
|
|
#include "FP_shift.h"
|
|
#include "FP_types.h"
|
|
#include "get_put.h"
|
|
/********************************************************/
|
|
|
|
extend(from,to,size)
|
|
_double *from;
|
|
EXTEND *to;
|
|
int size;
|
|
{
|
|
register char *cpt1;
|
|
unsigned long tmp;
|
|
int leadbit = 0;
|
|
|
|
cpt1 = (char *) from;
|
|
if (((DOUBLE *) cpt1)->_s.p1.fract == 0L) {
|
|
if (size == sizeof(SINGLE)) {
|
|
zero: zrf_ext(to);
|
|
return;
|
|
}
|
|
else if (((DOUBLE *) cpt1)->_s.p2 == 0L)
|
|
goto zero;
|
|
}
|
|
/* there is a number to convert so lets get started */
|
|
/* first extract the exponent; its always in the first two bytes */
|
|
|
|
to->exp = uget2(cpt1);
|
|
to->sign = (to->exp & 0x8000); /* set sign bit */
|
|
to->exp ^= to->sign;
|
|
if (size == sizeof(DOUBLE))
|
|
to->exp >>= DBL_EXPSHIFT;
|
|
else
|
|
to->exp >>= SGL_EXPSHIFT;
|
|
if (to->exp > 0)
|
|
leadbit++; /* will set Lead bit later */
|
|
|
|
to->m1 = get4(cpt1);
|
|
|
|
if (size == sizeof(DOUBLE)) {
|
|
to->m1 <<= DBL_M1LEFT; /* shift */
|
|
to->exp -= DBL_BIAS; /* remove bias */
|
|
cpt1 += 4;
|
|
tmp = get4(cpt1);
|
|
to->m1 |= (tmp>>DBL_RPACK); /* plus 10 == 32 */
|
|
to->m2 = (tmp<<DBL_LPACK); /* plus 22 == 32 */
|
|
}
|
|
else { /* size == sizeof(SINGLE) */
|
|
to->m1 <<= SGL_M1LEFT; /* shift */
|
|
to->exp -= SGL_BIAS; /* remove bias */
|
|
to->m2 = 0L;
|
|
}
|
|
|
|
to->m1 |= NORMBIT; /* set bit L */
|
|
if (leadbit == 0) /* set or clear Leading Bit */
|
|
to->m1 &= ~NORMBIT; /* clear bit L */
|
|
}
|